STDIN shouldn't have a per-line limit.

However, there may be a per-process limit to the amount of memory that you can use. Check out ulimit(1).

The little snippet below will print a string of about 80MB, then read it back into a single scalar in perl. I just tried this out on my workstation, and it seems to work just fine.

perl -e 'print "a"x85000000' | \
perl -e 'my $line = <STDIN>; print length($line), "\n";'
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